The Fast Marching Method: An Effective Tool for Tomographic Imaging and Tracking Multiple Phases in Complex Layered Media
The Fast Marching Method: An Effective Tool for Tomographic Imaging and Tracking Multiple Phases in Complex Layered Media
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DOI：
10.1071/eg05341
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发表时间：
2005-12
影响因子：
0.9
通讯作者：
N. Rawlinson;M. Sambridge
中科院分区：
文献类型：
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作者：
N. Rawlinson;M. Sambridge
地震传播时的准确预测在地震学的许多领域都是必需的，包括地震反射剖面的处理、地震定位和各种尺度的地震层析成像。在本文中，我们介绍了最近开发的基于网格的数值格式的两个地震应用，该格式通过eikonal方程的有限差分解来跟踪单调推进界面的演变，称为快速推进方法（FMM）。像大多数其他实用的基于网格的技术一样，FMM只能定位连续介质中的初到阶段；然而，它的无条件稳定性和快速计算的结合，使它成为一个真正实用的方案的速度场的任意复杂性。我们提出的FMM的第一个应用侧重于预测复杂二维层状介质中的多个反射和折射相位。通过将波前进入的每一层视为一个单独的计算域，我们表明FMM的顺序应用可用于跟踪由任意复杂性介质中任意数量的反射和传输分支组成的相位。我们还表明，在波前曲率高的源邻域中使用局部网格细化，可以显着提高方案的精度，并且很少额外的计算费用。我们考虑的FMM的第二个应用是在三维远震层析成像的背景下，它使用来自遥远地震的相对旅行时间残差来成像地震阵列下地壳和上地幔的波速变化。利用在塔斯马尼亚收集的远震数据，我们表明，FMM可以快速而可靠地计算出从撞击远震波前到位于地表的接收器阵列的两点旅行时间，尽管在中间的地壳和上地幔中存在显著的横向波速变化。结合快速子空间反演方法，证明了基于FMM的层析成像方案具有极高的效率和鲁棒性。
The accurate prediction of seismic traveltimes is required in many areas of seismology, including the processing of seismic reflection profiles, earthquake location, and seismic tomography at a variety of scales. In this paper, we present two seismic applications of a recently developed grid-based numerical scheme for tracking the evolution of monotonically advancing interfaces, via finite-difference solution of the eikonal equation, known as the fast marching method (FMM). Like most other practical grid-based techniques, FMM is only capable of locating the first-arrival phase in continuous media; however, its combination of unconditional stability and rapid computation make it a truly practical scheme for velocity fields of arbitrary complexity. The first application of FMM that we present focuses on the prediction of multiple reflection and refraction phases in complex 2D layered media. By treating each layer that the wavefront enters as a separate computational domain, we show that sequential application of FMM can be used to track phases comprising any number of reflection and transmission branches in media of arbitrary complexity. We also show that the use of local grid refinement in the source neighbourhood, where wavefront curvature is high, significantly improves the accuracy of the scheme with little extra computational expense. The second application of FMM that we consider is in the context of 3D teleseismic tomography, which uses relative traveltime residuals from distant earthquakes to image wavespeed variations in the Earth’s crust and upper mantle beneath a seismic array. Using teleseismic data collected in Tasmania, we show that FMM can rapidly and robustly calculate two-point traveltimes from an impinging teleseismic wavefront to a receiver array located on the surface, despite the presence of significant lateral variations in wavespeed in the intervening crust and upper mantle. Combined with a rapid subspace inversion method, the new FMM based tomographic scheme is shown to be extremely efficient and robust.